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(No lv io deLf G. A. BOYDEN. PNEUMATIC SIGNAL FOR RAILWAY TRAINS. No. 450,053. Patented Apr. 7,1891.

WITNESSES: I INVENTOR- ATTORNEY.

UNITE I STATES PATENT OFFICE,

GEORGE A. BOYDEN, OF BALTIMORE, MARYLAND, ASSIGNOR TO THE BOYDEN BRAKE COMPANY OF BALTIMORE CITY, OF SAME PLACE.

PNEUMATIC SIGNAL FOR 'RAILWAY-TRAINS.

SPECIFICATION forming part of Letters Patent No. 450,053, dated April '7, 1891. Application filed November 28, 1890. Serial No. 372,799. (No model.)

To all whom it may concern.-

Be it known that I, GEORGE A. BOYDEN, a citizen of the United States, residing at'Baltimore, in the State of Maryland, have invented certain new and useful Improvements in Pneumatic Signals for Railway-Trains, of which the following is a specification.

This invention relates to an improvement in pneumatic signals for railway-trains, and has for its object to counterpoise the signalvalve which controls the whistle, so as to impart to it any degree of sensitiveness that may be desired, and to use in connection with such valve a metal diaphragm arranged to 5 be as sensitive as the more flexible but perishable rubber diaphragms heretofore employed in this class of devices. Heretofore a single diaphragm has been employed with an artificially-created air-pressure acting directly in contact with its two sides. The objection to this is that too great a reduction of pressure in the train-pipe is required to unseat the valve which controls the whistle. Therefore I provide two diaphragms of unequal area, whereby the resistance of the whistle-controlling valve to unseat and also the resistance occasioned by the stiffness of the metal diaphragms are both effectually overcome.

- With these ends in View the invention will be fully described hereinafter, and pointed out in the claims. I In the accompanying drawings, which illustrate the invention, Figure 1 is an elevation, being a general view of the parts comprising the signal; and Fig. 2, a vertical longitudinal section of the signal-valve parts.

The letter A indicates the air-storage reservoir to be carried on the locomotive; B, the train-pipe leading therefrom; O, the signalvalve casing; D, the reducing-valve in the train-pipe between the storage-reservoir and signal-valve; E, the whistle on'a pipe E, leading from the signal-valve; I the flexible hoseconnection between the sections of the trainpipe; G, one of the escape-valves carried on the cars, and H the operating-cord connected with the lever of the escape-valve.

The signal-valve easing O is divided by two diaphragms M N, of unequal areas, into three 50 parallel chambers R, R, and S. The central chamber S is occupied by air at normal atmospheric pressure, and may have open ports a in its side walls, though this is unimportant. The two side chambers R R receive compressed air. One side chamber R is connected with the train-pipe B, and the other is connected with the whistle E by means of the pipe E. The diaphragm M, which covers the train-pipe chamber R, has a less area than the diaphragm N, which covers the whistle 50 pipe chamber R. This difference in the area of the diaphragms may be produced by any preferable means. In the present instance it is efiected by sloping the casing-walls, as at b, of the central chamber.

For convenience of attaching the dia phragms the signal-valve case is made in three sections, and each diaphragm is clamped between two sections, and the sections are secured together by bolts 0. A stemO extends through the centers of the diaphragms and is suitably secured thereto. At its lower end the stem fits in a socket d in the center of the bottom of the casing and is movable therein.

At its upper end the stemcarries a valve P, which seats against a tubular projection e at the end of a short tube Q, fitted in the top 'of the casing and communicating with a passage f, leading to the whistle-pipe E. An extension g projects from the valve and fits loosely within said tube and serves as a guide for the valve. The valve is made tight, when seated, by packing It.

An air-passage '0' extends through the center of the stem 0, and at its lower end has a port j, of less diameter than the said passage and opening into the train-pipe chamber R. The upper end of this passage is provided with out-lets 7c, opening into the whistle-pipe chamber R. It will thus be seen that the passage i affords direct communication between the two side chambers R R.

The train-pipe B is attached at opposite sides of the lower chamber R, and thus any variations of pressure in the train-pipe will 5 be felt on the diaphragm M, covering that chamber. The air from the train-pipe fills the chamber R and enters the small port j in the valve-stem and passes through the passage t' to the other chamber R, which is covered by the diaphragm N, and thus full pressure is also brought to bear upon one side of each diaphragm, and the pressure on the one acts in opposition to the pressure on the other. The resistance to movement of the valve P when on its seat, due to the atmospheric pressure on-one side and a greater artificial air-pressure on the other side, and also the normal stiffness of the diaphragm or diaphragms which operate the valve, is overcome by makingthe upper diaphragm M of greater area than the lower one, and thus the valve P is rendered more sensitive to slight reductions of pressure in the train-pipe. The variation or difference in area will be proportioned to the amount of the resistance referred to. Then the chambers R- R are filled with compressed air, the pressure on the lower diaphragm M, together with the resistance rethere is a pressure of forty pounds in the train-pipe and upon the diaphragms, a short quick pull upon the operating-cord H will open the escape-valve and reduce the pressure in the train-pipe and upon the lower diaphragm M to, say, thirty-nine pounds;- but a forty-pounds pressure will still be exerted upon the upper diaphragm, because the air cannot rush back into the lower chamber R before the diaphragms are moved and the valve unseated, owing to the small port j of the passage 2'.

lower and the aforesaid resistance together will overcome both, and the two diaphragms will be instantly lowered and the valve P unseated, whereupon air will rush from the chamber Rto the whistle; but the escape of this air will lower the pressure in the upper chamber R to thirty-nine pounds, the same as that in the lower chamber, and the valve thereupon will return to its seat. Thus it will be apparent that a short quick blast on the whistle will be given, exactlycorresponding to the actuation of the escape-valve G. Itwill be evident that the accomplishment of this result is due to the difference in area of the diaphragms, because the one being greater than the other the same air-pressure on each would obviously cause the diaphragm having the greater area to overcomethathaving the lesser area; but, taking into account the resistance referred to, and knowing what that resistance is, the difference between'the areas of the diaphragms can be so adjusted that the pressure on the diaphragm having the lesser area, together with the resistance, will slightly overbalance the diaphragm having the greater area, and thus the results previously explained can be brought about.

The pressure on the upper diaphragm being now greater than that on the- In the above description the respective dia phragms have been referred to as the upper and lower diaphragm for the purposes of explanation only. It is obvious that they may be otherwise arranged without affecting their operation or the operation of the valve. also obvious that the invention is not limited to the particular form of signal-valve shown.

A whistle has been referred to as the signal device; but other signal devices may be employed, such as a bell.

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent, is-

1. In a pneumatic signal, the combination of a signal-valve casing having two chambers, one provided with a connection for an airsupply and the other with a connection for a signal device, two diaphragms, each covering one of the chambers and said diaphragms having unequal areas, a valve, and a passage for the communication of compressed air from one chamber to the other.

2. In a pneumatic signal, the combination of a signal-valve casing having two chambers, oneprovided with a connection for an airsupply and the other with a connection for a signal device, two diaphragms of unequal areas, each covering one of said chambers and each exposed on one. side to atmospheric pressure, a valve, and a connection between the two diaphragms to cause them to coact.

3. In a pneumatic signal, the combination of a signal-valvecasing having two chambers, one provided with a connection for an airsupply and the other with a connection for a signal device, two diaphragms of unequal areas, each covering one of said chambers, a "alve, and a passage from the source of airsupply to furnish the air which operates the signal device.

4:. In a pneumatic signal, the combination of a signal-valve casing having two chambers, one provided with a connection for an airsupply and the other with a connection for a signal device, two diaphragms of unequal areas, each covering one of said chambers, and a valve for controlling the supply of air to the signal device and operated by the movement of said diaphragms.

5. In a pneumatic signal, the combination of a signal-valve casing having two chambers, one provided with a connection for an airsupply and the other with a connection fora signal device, two diaphragms, each covering one of the chambers, and said diaphragms having unequal areas, a valve, a. stem con- It is necting the two diaphragms, and an air-pasvalve, a passage from the source of air-supply to furnish the air which operates the signal device, and means to cause the diaphragms to coact.

7. In a pneumatic signal, the combination of a signal device, an air-pressure-supply pipe, signal-valve mechanism provided with two diaphragms of unequal area and each diaphragm covering a separate chamber and the chamber having the larger diaphragm communicating with the signal device and the chamber having the smaller diaphragm communicating with the air-supply pipe and the said chambers communicatingwitheach other, and a Valve controlling the exit of air to the signal device.

In testimony whereof I affix my signature in the presence of two Witnesses.

GEORGE A. BOYDEN. 

